Research will be carried out primarily in Chile at the University of Chile in collaboration with Dr. Andris Couve, as an extension of NIH grant R01 NS048045. GABA (gamma-aminobutyric acid) is the main inhibitory neurotransmitter in the mammalian nervous system. The slow action of GABA is mediate by GABAB receptors (GABABRs), which belong the group C G protein- coupled receptors. They function as heterodimers composed of GABABR1 and GABABR2 and couple to adenylyl cyclase, presynaptic voltage-gated Ca2+ channels and postsynaptic inwardly rectifying K+ channels. They have been implicated in epilepsy, nociception, depression and cognition. They also represent attractive targets for the treatment of withdrawal symptoms from addictive drugs such as cocaine. We suggest that GABABRs mediate their plethora of functions as part of multi-protein complexes that are subject to exquisite modulation. Thus we have proposed our general hypothesis: "GABABRs modulate the efficacy of inhibitory synaptic transmission as part of multi-protein complexes." Previous attempts at identifying these complexes have been only partially successful. We have now employed a unique approach to identify GABABR associated proteins in neurons using immunopurification and mass spectrometry. As a result we have obtained several candidates involved in protein turnover. To maximize the impact of our screen and open a new line of research we have prioritized the study of one candidate, namely dynamin-1, a protein with an established role in protein trafficking. Here we propose to investigate its role in GABABR turnover in the context of the following hypothesis: "Dynamin-1 defines the trafficking properties and membrane availability of GABABRs." We will develop the following specific aims: Specific Aim 1: Characterize the endocytosis of GABABRs in neurons. Specific Aim 2: Evaluate the specificity of the interaction to dynamin-1. Specific Aim 3: Test the functional consequences of the interaction to dynamin-1. Together with the parent grant, our proposed studies are likely to contribute to uncover novel mechanisms of trafficking and assembly of GABABRs into inhibitory sites and the identification of signaling events with potential therapeutic value. PUBLIC HEALTH RELEVANCE: Together with the parent grant, our proposed studies are likely to contribute to uncover novel mechanisms of trafficking and assembly of GABABRs into inhibitory sites and the identification of signaling events with potential therapeutic value.